This invention relates to a disc rotational driving device used for rotationally driving a disc-shaped recording medium such as an optical disc or a magneto-optical disc.
Conventionally, optical recording media such as optical discs and a magneto-optical discs have been used as recording media for information signals. Recording/reproducing devices for recording/reproducing information signals to/from such discs have been provided and broadly used.
In a recording/reproducing device of this type, a disc rotational driving device for positioning, holding and rotationally driving a disc is provided. The disc rotational driving device has a motor 103 which includes a case 101 having a rotor housed therein and a rotary shaft 102 attached to the rotor and having a part protruding outward from the case 101, as shown in FIG. 1.
At the distal end of the portion of the motor shaft of the rotary shaft 102 protruding from the case 101, a turntable 104 of an integral structure is mounted. This turntable 104 is formed in a substantially circular plate-like shape and has a center hole provided at its central part. The turntable 104 is mounted at one end of the rotary shaft 102 by having the rotary shaft 102 pressed into the center hole. At the center of the turntable 104, a protruding centering portion 105 is provided. This centering portion 105 is engaged with a positioning hole 202 provided at the center of a disc 201 and aligns the center of rotation of the disc 201 with the center of rotation of the turntable 104, thus centering the disc 201 on the turntable 104. As the inner circumference of the positioning hole 202 is placed on the circumferential surface of the centering portion 105 of the turntable 104, the disc 201 is positioned and thus held. By driving the motor 103 in this state, the disc 201 is rotationally driven together with the rotor, the rotary shaft 102 and the turntable 104.
In a recording/reproducing device having such a disc rotational driving device, an optical pickup device 203 is arranged to face the disc 201 which is rotationally driven by the rotation of the disc rotational driving device, and the signal recording area is scanned by a light beam emitted from the optical pickup device 203, thereby recording/reproducing an information signal.
In the recording/reproducing device having the disc rotational driving device as described above, a predetermined spacing must be formed between the disc 201 supported by the turntable 104 and the side of the case 101 of the motor 103, that is, the proximal end side of the rotary shaft 102 protruding from the case 101, because a disc loading mechanism including a disc tray for carrying the disc 201 into the recording/reproducing device from outside, the optical pickup device 203, and a guide shaft 204 or the like for supporting the optical pickup device 203 movably in the radial direction of the disc 201 are provided there.
Therefore, the rotary shaft 102 of the motor 103 must protrude from the case 101 by a predetermined length or longer. The turntable 104 must be mounted on the distal end side of the rotary shaft 102.
Since the turntable 104 is mounted on the distal end side of the rotary shaft, there is a long distance between the rotor housed in the case 101 of the motor 103 and the disc 201 supported by the turntable 104, and the rotor of the motor 103 and the disc 201 are connected with each other only by the rotary shaft 102. Therefore, the torsional rigidity of the whole system is lowered and a resonance frequency of torsional resonance is generated in a low-frequency band.
If a resonance frequency of torsional resonance is generated in a low-frequency band as described above, torsional resonance might be generated in the rotary shaft 102 or the like when the disc 201 is rotationally driven. Therefore, accurate rotation of the disc 201 is disturbed by such resonance.
In view of the foregoing status of the art, it is an object of the present invention to provide a disc rotational driving device which restrains torsional resonance generated in the rotary shaft of the motor as a driving source for rotationally driving the disc, and enables stable and accurate rotation of the disc.
A disc rotational driving device according to the present invention comprises: a motor in which a rotary shaft attached to a rotor housed in a case is provided to protrude from the case; and a turntable having a setting portion for setting a disc thereon and mounted on the proximal end side of the portion of the rotary shaft protruding from the case so as to cover the proximal end portion of the rotary shaft.
In this device, a positioning portion for positioning the disc is provided on the distal end side of the rotary shaft.
Another disc rotational driving device according to the present invention comprises: a motor having a rotary shaft attached to a rotor having a smaller diameter than the diameter of a disc; and a turntable having a setting portion for setting the disc thereon and a cylindrical portion provided to protrude inward, and mounted on the proximal end side of the rotary shaft so as to cover the proximal end side of the rotary shaft by the cylindrical portion.
The other objects and advantages of the present invention will be further clarified from the following description of the embodiment.